Five human deaths due to rabies were reported in the US in 2021, the highest annual case count in the last decade. Obviously, that’s still a very small number overall and pales in comparison to other infectious diseases in the US, and to rabies deaths in other parts of the world like Asia and Africa which are estimated to number in the tens of thousands every year. However, it’s still noteworthy as rabies is an almost invariably fatal infection that’s almost completely preventable in a country with resources like the US. Rabies vaccination is incredibly effective, as is rabies post-exposure prophylaxis (the series of antibody and vaccine injections someone should get after potential exposure) – when it’s given in a timely manner.

Knowing why these rabies deaths occurred is important for figuring out how to prevent more cases in the future.

Four cases involved exposure to bats. While canine rabies (the rabies strain that is adapted to and circulates in dog populations in some regions of the world) has been eliminated in the US and Canada, wildlife rabies remains a challenge. That’s particularly true with bats. While there are effective measures to help control rabies in terrestrial wildlife like raccoons (e.g. oral rabies vaccine baits such as ONRAB, which is produced here in Ontario), there are currently no effective means for controlling rabies in bats, even though the virus is endemic at a low level in virtually all bat populations in North America.  So there’s currently not much we can do about bat rabies except recognize the risk and try to prevent exposure (or respond when someone is exposed). That’s often the issue.

Three of the rabies deaths in the US in 2021 occurred over a 6-week period in the fall.  All three victims knew they had contact with a bat, but two of them released the bat (so there was no chance to test the animal for rabies), and they didn’t seek care for possible exposure. That typically happens when people don’t understand the issues with rabies and/or they don’t realize they were exposed. Bat bites can be very tiny and hard to detect (even when someone consciously comes in contact with a bat) but can still transmit rabies virus. One other person submitted the bat with which he had contact, but then declined post-exposure prophylaxis (even after the bat tested positive) because of a fear of vaccines (which begs the question as to why the bat was submitted for testing anyway…).

• These cases highlight ongoing knowledge gaps among the general public. Too many people don’t understand that bats are a source of rabies, that transmission can occur with even minor contact, that testing is available (and free), and that post-exposure treatment is available, safe and effective. Even when someone can’t submit the bat for testing, if they report significant exposure to a bat (e.g. direct contact) , they can recieve post-exposure prophylaxis as a precaution. So, all three of these deaths were avoidable.

An additional bat rabies death in Minnesota unfortunately shows why we have to say “almost” all cases are completely preventable. I haven’t found a primary report about this case, but various media articles indicate the victim was bitten by a bat, got post-exposure prophylaxis, but apparently had an unrecognized immune disease that hampered response to treatment, and therefor went on to develop rabies regardless and ultimately died.

The fifth case was a person who was infected with rabies by a dog.  While canine rabies strains have been eliminated from the US, it’s important to remember that dogs can still get infected with wildlife strains, and canine rabies is also widespread in many other parts of the world. An infected dog can pass any of these strains on to a person.  The victim in this case was bitten by a dog in the Philippines and developed rabies after returning to the US. Travellers too often don’t think about rabies, but massive numbers of individuals travel to rabies-endemic areas each year. Rabies vaccination is indicated in people who are likely to have  exposure to dogs during travel. However, the bigger issue is awareness in people who have unplanned encounters with dogs. People often don’t realize the risk of rabies exposure from contact with dogs in these countries, and don’t know what to do if they are bitten while traveling. Even if they don’t get treatment during their trip, most of the time they could get it once they return home, and it can still be effective as long as it’s given before the virus reaches the central nervous system (brain), which is when most signs of rabies start to appear. We want people to get treated promptly, but it can wait a short time if necessary (unless there’s exposure to the virus via the eyes… it’s a very short distance between the eyes and the brain). Yet, too often, bites don’t get reported and therefore treatment can’t be offered.

The common theme here is the need for public education. There’s limited penetration of rabies awareness education for the general public in North America. Travelers too often don’t get travel medicine consultations (and the quality of those, when it comes to zoonotic diseases, can be variable). A little knowledge can go a long way towards preventing rabies. The key is recognizing situations where exposure is possible, especially bat bites and bites from other wildlife rabies reservoir species (e.g. raccoons, skunks, foxes), and dog bites in areas where canine rabies is endemic. Bites from dogs in areas where canine rabies doesn’t exist are lower risk, but we still pay close attention to dog/cat bites because of the potential the dog/cat was exposed to rabies from wildlife. While that’s rare it still happens, and it’s why we need good rabies vaccine coverage in domestic dogs and cats, so that they don’t get rabies and then in turn transmit rabies to people.

Image: Anterior view of the face of a Myotis lucifugus, or little brown bat (source: CDC Public Health Image Library)